1. Field of the Invention
The present invention relates to a frame transmission apparatus and a method for checking normality in a frame transmission apparatus.
2. Description of the Related Art
As a technique for improving the quality of a communication path between communication apparatuses performing packet transfer, a link aggregation technique as described in Non-Patent Document 1 is known. Link aggregation is a technique of providing multiple physical links, such as cables, between neighboring communication apparatuses and bundling the physical links to form a virtual logical link. With the link aggregation, a communication path with a wider band can be obtained without preparing an expensive cable or communication interface. Also, since multiple physical links are used in parallel, even when part of the physical links has broken, complete disconnection of the communication path can be prevented, thereby improving availability of communication systems. In a communication system adopting link aggregation, a packet is transferred using one of multiple physical links.
Also, as a technique for maintaining networks for telecommunications carriers providing Layer 2 virtual private network (VPN) services, a function called Ethernet operations, administration, and maintenance (OAM) is known (Ethernet is a registered trademark). Ethernet OAM is standardized in Non-Patent Documents 2 and 3. In Ethernet OAM, a maintenance function point called a maintenance entity group end point (MEP) can be set. For example, a frame for maintenance management (hereinafter, referred to as a “maintenance management frame”) defined in Ethernet OAM is transmitted between two MEPs so as to check the normality of the frame transmission state between the MEPs.
[Non-Patent Document 1] IEEE Std 802.1AX -2008 Link Aggregation
[Non-Patent Document 2] ITU-T Y.1731, “OAM functions and mechanisms for Ethernet based networks” (“Ethernet” is a registered trademark)
[Non-Patent Document 3] IEEE Std 802.1ag Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management